(a) Field of the Invention
This invention relates generally to a chair and more particularly, to a chair control for the control of the tilting of tiltable chairs, particularly, stenographer's chairs.
(B) Description of the Prior Art
Stenographer's chairs comprise basically a stationary seat portion and a back portion which may or may not be tiltable. In the non-tiltable chair, the back is held securely by a one-piece bracket which is affixed to both the seat and the back portions of the chair.
In the tiltable chairs, the back portion of the chair moves rearwardly and downwardly when the user applies pressure to the back of the chair, this pressure being applied against a resisting force or biasing means which tends to return the back of the chair to the upright position when the pressure on the back of the chair is released.
The tiltable chair control of the prior art consists essentially of a fixed frame member which is mounted on a vertical post and which is attached to the undersurface of the seat of the chair and a movable frame member which is pivotally connected to the fixed frame member and adjustably connected to the back of the chair. A biasing means is provided which resists the backward and downward movement of the back of the chair from a defined normal vertical position and which returns the back of the chair to the normal resting position when the pressure is released.
The fixed frame member comprises a substantially flat plate which is secured to the undersurface of the seat and secured also to the vertical post. The movable frame member is secured to the fixed frame member behind the vertical post and pivots on a horizontal bolt. A biasing means or return control means is affixed to the rear portion of the fixed frame member passing vertically through the movable frame member and the biasing means comprises a vertical bolt and a helical spring inserted thereon. When rearward pressure is applied to the back of the chair, the movable frame portion pivots on the horizontal bolt and depresses the spring on the vertical bolt. The movable frame portion carries an upper flat plate across the front top portion thereof. The helical spring is inserted on the bolt from the bottom end and its upper end rests on the undersurface of this upper flat plate of the movable frame member. Thus, when the back of the chair is tilted backward, movement of this upper flat plate downward causes the helical spring to contract. When the pressure in the back of the chair is removed, the tension in the spring causes the spring to expand forcing the movable frame member back to the original resting position. In this position, the top surface of the upper flat plate of the movable frame member is in contact with the rear portion of the fixed frame member and therefore no further upwards movement of the movable frame member can occur.
When the pressure on the chair back is released, the tension in the compressed spring causes the back of the chair to return to the normal position. A handwheel to adjust the amount of tension in the helical spring when in the resting position is provided underneath the spring. The tension in the resting helical spring may be adjusted by the user thereby adjusting the amount of force required to tilt the back of the chair.
The movable frame member of the chair controls of the prior art comprise a first bracket pivotally connected to the fixed frame portion, a second bracket adjustably connected to the first bracket and a seat back portion which is affixed to the second bracket. The adjustable connection between the first bracket and the second bracket allows the user of the chair to adjust the position of the back of the chair in the resting position. The two brackets are usually connected (at the front of the second bracket and at the middle of the first bracket) by a horizontal bolt extending through the arms of the brackets and a tightening means comprising an adjustable handwheel. The second bracket may have an arc-shaped aperture in the forward side portions thereof so that when the tightening means is loosened, the position of the second bracket and therefore the position of the back of the chair may be adjusted with respect to the first bracket. Once the adjustment is made, the tightening means is secured. The problem is that with continual use of the chair, the tightening means becomes loosened and requires constant adjustment. Tightening this means causes the arms of the first and the second bracket to be bent inward thereby distorting its structure and causing eventual breakage.
A second problem of these controls is the shape of the vertical bolt. As the back of the chair is depressed rearward and downward, and the helical spring is contracted, the vertical bolt must pivot slightly. However, no provision has been made for this pivoting of the bolt and consequently, a wearing of the bolt and the fixed frame occurs which leads to a deterioration of the operation of the control.
A third problem of these controls is their appearance. In order to provide a pivotal connection between the fixed frame member and the movable frame member which is strong enough to sustain constant movement, a rather large mechanism was needed. Consequently, in order to provide sufficient resistance to the movement of the movable frame member and to urge it back to the normal position, a large helical spring was provided on a bolt to which a large circular handle was attached for adjusting the tension in the spring. This rather cumbersome arrangement deteriorated from the appearance of the chair.
Accordingly, it is an object of the present invention to at least partially overcome these disadvantages by providing a novel chair control for a stenographer's chair which utilizes a strong and efficient stopping means to arrest the movement of the movable frame member against the fixed frame member in an efficient manner which does not lead to the deterioration of the control.
A further object of the present invention is to provide a novel pivoting means with a provision for the pivoting of the bolt when the seat back is depressed.
A still further object of the present invention is to provide a pivotal connection between the fixed frame member and the movable frame member which is strong enough to sustain constant pressure and movement but compact enough to be attractive in appearance.
A further object of the invention is to provide a novel construction for the first bracket of the movable frame member of the chair control to provide strength to the member and prevent breakage of the control.
Another object of the present invention is to provide a novel adjustment means for adjusting the novel tension control or biasing means which does not require any other tools and may be operated easily for quick adjustments to the chair.